The mourning period for Thailand's late king Bhumibol Adulyadej is coming to an end, ahead of his cremation later this month.

Tens of thousands of mourners have been rushing to Bangkok's Grand Palace to pay their respects, as a period of nearly a year for his body to lie in state ends ahead of the October 26 cremation.

Since Bhumibol's death last October 13 at the age of 88, more than 12 million people have visited the golden Dusit Maha Prasat Throne Hall, where the late monarch's coffin is kept behind a symbolic royal urn.

The hall is to be closed to visitors at midnight on Thursday.

The throne hall has been kept open 24 hours a day since last Saturday to accommodate the high number of last-minute mourners.

Officials said the palace received over 96,000 visitors on Wednesday, a record number for one day.